1. Field of the Invention
The present invention relates to a device for creating print data utilized by a printer. The present invention further relates to a method for creating print data and a computer program product for creating print data. Further, the present invention relates to a computer program product manufacturing method. The printer of the present specification includes all devices for printing words or images onto a print medium. For example, the printer of the present specification includes ink jet printers and laser printers. Ink jet printers and laser printers include copying machines, fax machines, multifunctional products, etc.
2. Description of the Related Art
A printer utilizes colorant such as ink, toner, etc. to form points on a print medium. Desired words or images are thus formed on the print medium. In the present specification, a point formed on a print medium by a printer utilizing colorant is termed a dot. For example, in the case of an ink jet printer, a point formed on a print medium by discharging a droplet of ink from a nozzle toward the print medium is termed a dot. Furthermore, a point formed on a print medium by discharging a plurality of ink droplets onto the same location on the print medium from one or a plurality of nozzles is also termed a dot.
An ink jet printer discharges ink droplets from nozzles towards a print medium, thus forming dots on the print medium. The ink jet printer may be utilized while connected with an external device such as a personal computer, or the like. In the case where an image shown on a display of the personal computer is to be printed by the ink jet printer, the personal computer creates bit-mapped data. The created bit-mapped data includes color information of each coordinate. In the case of a color image, the color information of the bit-mapped data is represented as a combination of color and color density of that color. Consequently, bit-mapped data of the color image includes a plurality of combinations of coordinate, color, and color density. Further, in the case of a monochrome image, the color information of the bit-mapped data can be represented as a combination of single color and color density, or can be represented only as color density. The bit-mapped data of the monochrome image includes a plurality of combinations of coordinate, single color, and color density (or a plurality of combinations of coordinate and color density).
The personal computer chooses coordinates at which dots will be formed from the bit-mapped data. This process is performed based on the color information of the coordinates included in the bit-mapped data. The coordinates are chosen from the bit-mapped data using, for example, the halftone process or the dither method. The personal computer outputs the information representing the chosen coordinates to the ink jet printer. Here, this information is termed print data. The print data for color printing can be formed from, for example, combinations of a chosen coordinate and color (for example, any one out of cyan, magenta, yellow, and black). The ink jet printer receives the print data output from the personal computer, and forms dots based on the print data that has been received. For example, in the case where a combination of the coordinate (x, y) and yellow is included in the print data, the ink jet printer forms a yellow dot at the coordinate (x, y).
FIG. 18 is a figure schematically showing an example of dots 100 formed by the ink jet printer. In the example shown in FIG. 18, the dots 100 are formed in 8 rows×8 lines. The dots have not been filled with ink in FIG. 18. The numbers shown above the dots 100 are row numbers, and the numbers shown to the left of the dots 100 are line numbers. Two dots 100 that adjoin in the row direction or line direction overlap. The arrow A in the figure shows the direction of movement of the print medium with respect to the nozzles. Below, eight dots aligned in the A direction will be termed a dot row, and eight dots aligned in a direction orthogonal to the A direction will be termed a dot line. In this example, eight dot rows and eight dot lines are formed. Below, the rows will be represented as x coordinates and the lines will be represented as y coordinates. Sixty four coordinates (1, 1), (1, 2), etc. are included in the print data being utilized to form the dots 100 shown in this example.
Ink is discharged from the nozzles while the print medium is moving with respect to the nozzles in the direction of the arrow A. For example, the eight dots of the first dot row are formed by continuously discharging ink droplets from one nozzle while the print medium is moving with respect to the nozzle in the direction of the arrow A. Similarly, the eight dots of the second dot row are also formed by continuously discharging ink from one different nozzle. Eight nozzles that are offset in an X direction are required to form the eight dot rows shown in FIG. 18. All the dots 100 are formed uniformly in the example shown in FIG. 18, and printing could be termed satisfactory.
However, the timing at which ink is discharged from a certain nozzle may be earlier or later than the intended timing. In this case, the dot row formed by this nozzle is formed at a position that is displaced with respect to the dot rows formed by the other nozzles. FIG. 19 shows an example of the dots 100 where the dot rows were formed by eight nozzles that include a nozzle discharging ink at a timing later than the intended timing. In this example, the nozzle for forming the fifth dot row discharges ink at a timing later than the intended timing. As a result, the fifth dot row is displaced upwards. Here, satisfactory printing results cannot be achieved.